1. Field of the Invention
This invention relates to security systems and methods for integrated circuits, and more particularly to systems and methods for protecting integrated circuit systems from unauthorized copying and for controlling their use.
2. Description of the Related Art
One of the major problems with integrated circuits (ICs) is in providing security for both the design and use of the circuits themselves and for systems which incorporate the circuits. It is possible to reverse engineer most (ICs) simply by sectioning the device, photographing its circuitry and fabricating duplicate circuitry from the photographs. The copier can thus obtain the benefit of the completed circuit design at a small fraction of the cost involved in the original design.
Controlling the use of systems which incorporate ICs is another persistent problem and need. For example, it would often be desirable to base license fees for software/hardware systems upon the number of times the system is used, or the duration of system use. However, no reliable and secure method is currently available for the licensor to remotely monitor the use of many different licensed systems. Another example of the need for use control is that often a supposedly secure computer system will have numerous different entry points, each of which is provided with a control mechanism which is accessible only by authorized persons. However, if an unauthorized individual obtains the necessary information or equipment to gain access to one of the entry points, that same information or equipment might be used to gain access to the other entry points and thereby compromise the entire system. A similar problem exists in the case of IC systems which are produced in quantity, each system having the same security mechanism. Once one of the systems is comprised by obtaining unauthorized access, all of the other systems are similarly compromised.